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Median of three uniforms below two thirds

Question

Three independent values are drawn from the uniform distribution on [0,1][0,1]. Find the probability that the middle value, once they are sorted, is smaller than 23\tfrac23.

Short answer

2027\tfrac{20}{27}. The median is below 23\tfrac23 exactly when at least two of the three values are, a binomial event with success probability 23\tfrac23: (23)3+3(23)213=827+1227=2027\big(\tfrac23\big)^3+3\big(\tfrac23\big)^2\tfrac13=\tfrac{8}{27}+\tfrac{12}{27}=\tfrac{20}{27}.

Adapted from QuantQuestions.io; question and answer rewritten by SelfMadeQuant.com.

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